Hitherto, optical discs such as DVD (Digital Versatile Disc), etc. are used as recording media for information signal. In order to perform recording of information signals onto optical discs of this kind, or to perform reproduction of information signals recorded on the optical discs, optical pick-up is used.
Such an optical pick-up comprises an actuator for focus which is adapted for moving an object lens in a focus direction which is an optical axis direction thereof in order to allow light beams emitted from a light source to be in-focus state onto the recording surface of the optical disc, and further comprises an actuator for tracking which is adapted for moving the object lens in a tracking direction at the plane surface direction perpendicular to the optical axis thereof in order to allow light beams to follow recording tracks provided at the optical disc. Namely, the optical pick-up comprises a biaxial actuator for allowing the object lens to undergo drive displacement in biaxial directions perpendicular to each other of the focus direction and the tracking direction.
In recent years, with realization of high recording density of the optical discs, it is required to allow shape of light spot formed on the recording surface of the optical disc to be more precise circular. It is more important to conduct a control such that the optical axis of the object lens is perpendicular to the recording surface of the optical disc. For this reason, there is proposed an optical pick-up comprising a triaxial actuator in which an actuator dedicated for tilt angle control for tilting the optical axis of the object lens in a manner following inclination of the optical disc is added to a biaxial actuator for focus and tracking.
As an optical pick-up comprising such triaxial actuator, there is an optical pick-up adapted for supporting a lens holder which has supported an object lens by a shaft to rotate the lens holder with the support shaft being as fulcrum to thereby adjust inclination (tilt) with respect to the optical disc of the object lens. For example, there is an optical pick-up described in the Japanese Patent Application Laid Open No. 1997-44879 publication.
This optical pick-up serves to rotate the lens holder by drive force based on magnetic interaction between drive current delivered to coil provided on the peripheral surface of the lens holder and magnetic flux produced from magnet provided in a manner opposite to the coil to thereby tilt the object lens supported by the lens holder to perform control of tilt angle.
Meanwhile, in the optical pick-up adapted for rotating the lens holder by supporting mechanism using the shaft, the lens holder becomes difficult to undergo rotation displacement in a manner following a drive force by hysteresis based on sliding friction produced between the shaft and bearing for supporting such shaft. As a result, it becomes impossible to perform control of tilt angle of the object lens corresponding to drive current delivered to the coil in accordance with a control signal.